Circuit interrupter



Jan. 12, 1937.

F. KESSELRING ET AL CIRCUIT INTERRUPTER Filed NOV. 15, 1934 PatentedJan. 12, 1937 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTEB ration ofPennsylvania.

Application November 13, 1934, Serial No. 752,820 In Germany November17, 1933 Z Claims.

Our invention relates to circuit breakers of the type wherein a flowingstream or jet of suitable arc extinguishing fluid is used forextinguishing the arc which is established incident to the opening ofthe controlled circuit. One common form ci such breakers comprises areservoir, wherein a quantity of are extinguishing gas is containedunder pressure, an arc chamberyand means for causing a predeterminedvoiumeof the gas contained in the reservoir to iiow through thearcchamber during each circuit opening operation. The primary object ofthe present invention is tc improve the operation of devices of thistype through the provision of means for most effectively utilizing theilowing stream of arc extinguishing fluid and for preventing theutilization of a larger quantity of this fluid than is necessary duringthe operation of the breaker.

Heretofore, it has been customary to connect the passage or chamberwherein the arc is established directly with the source of the arcextinguishing fluid, andimmediately upon the occurrence of an overloadcondition, the arc ex tinguishing fluid was caused to flow through thearc passage at a substantially constant rate. In order to assuresatisfactory operation of these devices over the wide range of arccurrents which are encountered in ordinary service, it was necessarythat the rate of flow of this stream of arc 3o extinguishing huid besuiiiciently high to assure the extinction of the largest magnitude arcwhich might be drawn within the arc passage during the operation of theinterrupter. On low currents, this arrangement proved itself wasteful ofthe are extinguishing iluid, due primarily to the fact that satisfactoryextinction of low current arcs could be effected with a much smallerquantity of fluid and with a much lower rate of flow. Not only did theprior art devices utilize an 4o excessively large amount of arcextinguishing fluid during the extinction of low and moderate currentarcs, but in addition, they did not eiliciently utilize the fluidflowing therethrough even when extinguishing large current magnitudearcs. The extinction of short arcs, regardless of their currentmagnitude, may be effected through the use of a low velocity stream ofarc extinguishing uid with practically the same degree of eiilciency asis attained through the use of a high velocity stream of arcextinguishing fluid. As the arc lengthens, however, the high velocitystream becomes more eiilcient. Thus a device which utilizes a constantvelocity stream of arc extinguishing fluid utilizes that streamemciently only during the final stages of the circuit opening operation,i. e. when a relatively long arc has been drawn within the arc chamber.

In overcoming these disadvantages, the present invention provides meansfor so controlling the flow of the arc extinguishing fluid that the 5amount used is restricted to not more than is necessary during theextinction of low magnitude current arcs and the maximum rate of flow isutilized only during the extinction of large current magnitude arcs; andeven then the maxi- 10 mum rate of ilow is caused to take place onlywhen the arc drawing contact members have separated a sufficientdistance to assure an etilcient utilization of the arc extinguishingproperties of the high velocity stream. By this ar- 15 rangement thevolume of arc extinguishing fluid utilized during the normal operationof the breaker is substantially reduced, and a further object of ourinvention, namely the minimizing of the physical dimensions of the arcextinguishing iluid 20 reservoirs which are utilized with circuitinterrupters of the type under considerationl is accomplished. A

An ancillary object of our invention is to provide a -circuitinterrupter of the type discussed 25 above, which shall be simpler indesign. more reliable and efficient in operation, and less expensive tomanufacture than the previously known devices of this type, the improvedoperation to be brought about through a novel arrangement ol.' 30 theseveral parts of the interrupter.

These and other objects oi our invention will be made more apparent byreference to the following drawing and description oi' a circuitinterrupter embodying the features of the inven- 35 tion. Referring tothe drawing:

Figure 1 is a side elevational view, partially in section, of a highcapacity circuit breaker constructed in accordance with our invention; I

Fig. 2 is an elevational view of the circuit in- 40 terrupter shown inFig. 1;

Fig. 3 is a fragmentary sectional view on the line III-111 of Fis. 1;

Fig. 4 is a fragmentary view o'f the arc passage A and contact structureof the interrupter shown in 45 Fig. 1, the contacts are shown in apartially open position;

Fig. 5 is a curve showing the variation in the amount and the rate oi'now of the arc extinguishing medium with respect to time, during the 50operation of a circuit interrupter constructed according to ourinvention; and,

Fig. 6 is a schematic view o1 one form of control circuit for theinterrupter shown in Figs. 1 through 4. 55

As shown particularly in Figs. l, 2, and 3, the preferred form of ourinvention includes a base I, upon which are mounted a pair oi supportinginsulators 3 and 5. The lower insulator 5 is adapted to support apressure tank 1 which serves as a reservoir for containing the arcextinguishing fluid utilized for extinguishing the arc establishedincident to each circuit opening operation of the breaker. The upperinsulator 3 supports a metallic housing 9 which defines the Walls of anexpansion chamber IU into which the arc extinguishing fluid ilows duringthe operation of the breaker.

The housing 9 is substantially cylindrical in form and is closed at itsupper end by a cap member II, which is affixed thereto by any suitablemeans. An insulating conduit I3 is supported upon the pressure tank 1and serves to conduct the arc extinguishing fluid contained therein tothe arc passage I1, the walls of which are defined by a secondinsulating conduit I5 having the same internal dimensions as the lowerinsulating conduit I3 and the cylindrical housing 9.

An electro-magnetic valve I9, positioned intermediate the ends of thelower insulating conduit I3, is provided for controlling the flow of arcextinguishing fluid therethrough, and a plate member 2| of conductingmaterial, which serves to support a hollow contact member 23, ispositioned between the lower insulating conduit I3 and the member I5which defines the walls of the arc passage. I1. All of the connectionsbetween the pressure chamber 1, the insulating conduit I3 leadingtherefrom, the member I5 which defines the arc passage I1, and the uppercylindrical member 9 which serves as the expansion chamber, aregas-tight, in order to prevent leakage of the arc extinguishing fluidduring the operation of the apparatus.

A rod-shaped contact member 25 is provided for cooperating with thepreviously mentioned hollow contact member 23 in order to permit theopening and the closing of the electrical circuit through the breaker.This rod contact member 25 is supported upon a piston 21 which isadapted to move Within the upper cylindrical member 9 and iselectrically connected to the cap II, which closes the upper end of thatmember, by means of a flexible shunt 29. A tension spring 3|, one end ofwhich is affixed to the cap member II and the other end of which isaiixed to the piston 21, biases the movable contact toward the opencircuit position.

The piston 21, or someportion thereof, is made of magnetic material, anda coil member 33, disposed bout the upper cylindrical member 9, isprovided for attracting this piston, in order to move the contacts tothe closed circuit position. It is, of course, necessary that the member9 which defines the walls of the cylindrical chamber III wherein thepiston 21 moves shall be formed of non-magnetic material. Suitableterminals 35 are afiixed to the cap member II, and to an outwardlyprojecting member 31 formed integral with the plate 2| for connectingthe breaker into an electrical circuit.

In the particular breaker disclosed in the drawing, compressed air isutilized as the arc extinguishing fluid. This substance is usedprimarily because of its low cost, its universal availability, and itsgood arc extinguishing properties. It is, o! course, within the provinceof our invention that other gases. or even liquids or vapors,

might be used with an equal, or possibly better, degree of efiiciency.'I'he invention is primarily considered with the manner in which the arcextinguishing fluid is caused to flow through the arc passage during theoperation of the device, and the particular fluid which is used is notan important part of the invention.

A compressor 39, which is disposed within the pressure tank 1, and isconnected to the outer atmosphere, by a suitable conduit 4I, is providedfor restoring the arc extinguishing fluid to the pressure tank 1,following each operation of the breaker. The compressor 39 is preferablyoperated by a motor 43, which is controlled by a pressure-responsiverelay 46 positioned in the Conduit 4I intermediate its ends.

The electro-magnetic valve I9, which is disposed in the conduit I3leading from the pressure tank 1 to the arc passage I1, is normallyclosed, in order to prevent any flow of the arc extinguishing iiuid fromthe pressure tank 1 except during the circuit opening operation of thebreaker. This valve I9 may be actuated through the operation of theoverload relay which brings about the opening of the interrupter or byany other similar means. It is preferably provided with a potentialmeans (not shown) normally electrically connected across the arc bysuitable leads 42 for causing the valve to close immediately the arc isextinguished within the interruptor.

The cylindrical member 9 is provided with a plurality of vent openingsor ports 44 which are so positioned that they are not uncovered by theupwardly moving piston 21 until the final stages .of the circuit openingoperation. Through this arrangement the rate of now of the arcextingushing fluid is caused to vary in two successive steps during theprogress of the circuit opening operation.

A suitable control circuit is shown in Fig. 6. This circuit includes athree-position switch 45, an overload relay 41, and suitable conductingmeans for completing the electrical circuit to the various parts. Thecontrol circuit is so arranged that the breaker may be opened or closedthrough the actuation of the three-position switch, provided that anoverload capable of actuating the relay 41 does not exist in the powercircuit. If such an overload occurs when the interrupter is in theclosed circuit position, it will, of course, automatically open.

The circuit interruptor is shown in the closed circuit position in Figs.1 and 6. Upon the occurrence of an overload, capable of effecting theactuation of the overload relay 41, the armature 49 of that relay ismoved upwardly so as to open the circuit between the contact points 5Iand 53 and close the circuit between the other two contact points 54 and55. This eiects a deenerglzation of the closing coil 33 and asimultaneous energization oi the electro-magnetic valve I9. Immediatelyupon the deenergization of the holding coil 33, the spring 3i begins tomove the piston member 21 and with it the movable contact rod 25 towardthe open circuit position, thereby effecting the separation of thecooperating contact members 23 and 25, and the establishing of an arcwithin the arc passage I1. The opening movement is aided by the pressureof the arc extinguishing fluid since the actuation of theelectro-magnetic valve I9, which occurs simultaneously with theinitiation of the contact separating movement, causes a quantity of thearc extinguishing fluid to move through the hollow contact member 23into the arc passage I1, and to exert a force against the piston 21tending to move that member in the expansion chamber IU.

Suitable vent openings 51 in the cap II prevent any gas which may beentrapped in the expansion chamber I9 from impeding the free movement ofthe piston 21.

The amount of arc extinguishing fluid which flows through the hollowcontact member 23 into the arc passage I1 during the period of timerequired for the piston 21 to move from the position shown in Fig. l tothe position shown in Fig. 4 is, of course, a function of the volume ofthe arc passage I1, the dimensions of the hollow contact 23, the volumeof the expansion chamber I made available by the upward movement of thepiston 21, and the pressure maintained within the tank 1. Preferably,these several quantities are so correlated that rapid and emcientextinction of all except the largest current magnitude arcs is effectedbefore the ports I4 are uncovered by the upwardly moving piston. If thishas been done the amount of arc extinguishing iluid which is used duringeach circuit opening operation may be substantially minimized, ascompared with the previously known devices, without any decrease in theoperating eiilciency of the breaker.

The amount of arc extinguishing fluid which may be caused to flowthrough the arc passage I1 prior to the time that the ports M formed inthe side walls of the expansion chamber I0 are uncovered by the upwardlymoving piston 21 is obviously limited to a definite value. Further,since the volume of the arc passage I1 and the volume of the expansionchamber III which is opened by the upward movement of the piston, isalso a fixed quantity, the rate of flow of the arc extinguishing fluiddecreases from a predetermined maximum value to a less value during thisstage of the circuit opening operation. 'Ihis decrease resulting fromthe increase in back pressure is caused by the ow of gas into the closedarc passage I1 and expansion chamber I0. For

all ordinary values of arc current, this initiall quantity ofarcextinguishing fluid is sufiicient to effect the extinction of the arcand irrimediately the arc is extinguished, the potential unit of theelectro-magnetic valve I9 which is connected across the terminals of theinterrupter effects the closing of that valve, thereby preventingfurther flow of the arc extinguishing fluid.

If, however, this initial flow of arc extinguishing uid is incapable ofeffecting the extinction of the are before the ports Il 'are uncoveredbythe upwardly moving piston 21, the uncovering of those portsimmediately causes a very substantial reduction in the back pressureopposing the ow of the 'arc extinguishing uid through the arc passageI1, and thereby brings abouta very substantial increase in the rate ofilow of the arc extinguishing fluid through the arc passage. When theports .Il are completely opened, the back pressure existing in the arcpassage I1 is not substantially greater than atmospheric and the arcextinguishing uid thus flows through the hollow contact 23 into the arcpassage I1 with the maximum possible velocity, and brings about theextinction of the arc within a short interval of time. Immediately uponthe extinction of the arc, the potential element of the electromagneticvalve I9 effects the closing of the conduit I3 leading to the pressurechamber and thereby cuts on the flow of the arc extinguishing uuid.

. By making the hollow-contact 23 the only inlet into the arc passageI1, an intimate intermixing of the arc extinguishing fluid with the arcstream is assured at all times during the operation of the interrupter.The total area of the ports M which are opened in the expansion chamberIII during the circuit opening operation of the breaker must bedetermined for each installation wherein the invention is embodied.Similarly, the interval vof time which elapses before the arcextinguishing fluid is caused to flow at its maximum possible rate mustbe determined in accordance with the requirements of the circuit onwhich the breaker is used.

The curve in Fig. illustrates the variation in the rate of flow of thearc extinguishing gas during the operation of the interrupter. Theportion of the curve between A and B illustrates how the rate of flowfalls off slightly while the piston is moving upwardly in the expansionchamber, and the increase in the slope Vof the curve between the pointsB and C illustrates the increase in the rate of iiow which accompaniesthe opening of the ports I4 within the expansion chamber. No attempt hasbeen made in this curve to attach any quantitative values to theconditions portrayed. It merely serves to illustrate, in a generalmanner, the variation in the rate of flow of the arc extinguishing fluidduring the circuit opening operation.

To open the circuit manually, the three position switch I5 is moved fromthe position shown in Fig. 6 to a position where the contact arm engagesthe second contact point 60. This effects a deenergization of theclosing coil 33 and a simultaneous energization of the electro-magneticvalve I 9. The opening operation then proceeds in exactly the samemanner as described above. If it is desired to leave the breaker in theopen circuit position for an extended period of time, the switch 45 ismoved to the third contact point 62, at which time the operating elementof electro-magnetic valve I9 and the closing coil I3 are entirelydeenergized. The pressure-responsive relay II and the compressor motor42 are ordinarily connected in the circuit at all times, in order toassure that adequate supply of arc extinguishing iluid shall beavailable for the operation of the breaker.

In the foregoing, we have pointed out how the rate of flow of arcextinguishing iluid through the arc passage of a circuit interrupter maybe caused to vary during the operation of the breaker, in order toprevent the use of unreasonably large quantities of arc extinguishingfluid and to make possible a more emcient operation of the device. Inthe preferrediorm of our invention, a predetermined small quantity ofarc extinguishing fluid is caused to ow through the arc passage duringthe initial stages of the circuit opening operation, and if this ow doesnot effect the extinction of the arc a further quantity of fluid is thencaused to flow through the passage at an increased rate oi flow, thislatter iiow continuing until the arc is extinguished. As a further meansfor assuring emcient use of the arc extinguishing fluid in the structureof our invention, we have provided means for causing the maximum rate offlow of the arc extinguishing iiuid to be attained only when the contactmembers have been separated a sumcient distance to make possible anemcient utilization of that rate of ow. This prevents 4waste oi the arcextinguishing fluid without any sacrifice of arc extinguishing capacity.

While in the foregoing we have pointed out the details of a preferredembodiment of ourrinvention, it is to be understood that many of thesedetails are merely illustrative, and that variations in their preciseform will be both necessary and desirable in certain instances. It isour desire, therefore, that the language of the accompanying claimsshall be accorded the broadest reasonable construction, and that ourinvention shall be limited only by what is expressly stated therein andby the prior art.

We claim as our invention:

1. In a circuit interrupter, means for defining the walls of an arcpassage which is substantially completely enclosed during the operationoi' said interrupter except for an inlet and an outlet opening,separable contact means for establishing the arc incident to eachopening operation of said interrupter Within said arc passage, aquantity of arc extinguishing fluid, means whereby said arcextinguishing fluid is admitted to said arc passage through said inletopeningat a substantially uniform inlet pressure during the operation ofsaid interrupter, and throttling means for coacting with said outletopening during each opening operation of'said interrupter to restrictthe rate of flow of said fluid into said arc passage until said contactshave separated a predetermined distance.

2. In a circuit interrupter comprising separable contact members, anenclosed arc passage associated therewith, and a supply ofarc-extinguishing fluid confined under pressure, the combination ofmeans for admitting said fluid into the passage at one rate during theinitial stages of contact separation and for substantially altering saidrate as the distance of contact separation increases.

3. In a circuit interrupter comprising separa. ble contact members, anenclosed arc passage lassociated therewith, and a supply ofarc-extinguishing fluid conned under pressure, the combination of meansfor admitting said uid into the passage at one rate during the initalstages of Contact separation and for substantially increasing said rateas the distance of contact separation increases.

4. In a circuit interrupter comprising separable contact members, anenclosed arc passage associated therewith, and a supply oi'arc-extinguishing fluid confined under pressure, the combination ofmeans for admitting the fluid into the passage at one rate during theinitial stages of contact separation, and means responsive to a failureof said fluid to extinguish the arc during said initial stages foradmitting further fluid at a substantially more rapid rate as thedistance of contact separation increases.

5. A circuit interrupter comprising a. pair of separable contact membersone of which is provided with a central opening and the other of whichis adapted to close said opening during engagement, an enclosed arcpassage utilizing the centrally-opened contact member as one of its endwalls and completely surrounding the cooperating separable member, asupply of arc-extinguishing fluid confined under pressure, meansresponsive to a separation of said contact members for allowing saidfluid to fiow into the arc passage through said contact opening, andmeans for increasing the rate of said flow when the distance ofseparation of the contacts attains a given magnitude.

6. A circuitvinterrupter comprising a pair of separable contact membersone of which is provided with a central opening and the other of whichis adapted to close said opening during engagement, an enclosed arcpassage utilizing the centrally-opened contact member as one of its endwalls and completely surrounding the cooperating separable member, asupply of arcextinguishing fluid confined under pressure, meansresponsive to a separation of said contact members for allowing saidfluid to flow into the arc passage through said contact opening, andmeans responsive to a failure of said fluid to extinguish the arc duringthe initial stages of contact separation for admitting further fluid ata substantially more rapid rate as the distance of said contactseparation increases.

7. In a circuit interrupter comprising a pair of separable contactmembers, an enclosed arc passage associated therewith, and a supply ofarc-extinguishing iiuld confined under pressure, the combination ofmeans for admitting said fluid into'the passage at a comparatively slowrate during the initial stages oi' contact separation and further meansfor substantially increasing said rate as the distance of contactseparation increases, said further means comprising an expansion chamberconnecting with said arc passage, said chamber being closed except for avent port in the side wall thereof, and a piston so movable therein asto uncover said port when the distance of contact separation attains agiven magnitude.

FRITZ KESSELRING. FRIEDRICH BEGRICH.

